Typically you will not put a "many" property in the select clause but rather in a join()... but if you do you'll get an error.
In the example below "details" is a one to many property on bug.
Query<Bug> query = Ebean.createQuery(Bug.class); query.select("title, details"); query.findList();
// the above will error...
Query<Bug> query = Ebean.createQuery(Bug.class); query.select("title"); query.join("details"); query.findList();
The fix is to override in BeanPropertyAssocMany the appendSelect() and readSet() methods.